Jan 1, 1970

Newbie question. In a number of my contacts I have seen recently Jan 1, 1970 as listed for their birthday, anniversary or both. When I go to edit the contact it doesnt show up in an editable field, so I cant delete the date. I tried looking at the sources where my contacts data is being pulled from and that date isnt in any of them. Anybody know what this is and more importantly how to fix it. Thanks in advance